Molecular Mechanism of Selenium Affecting the Synthesis of Flavonoids in G. biloba Leaves

Plant Molecular Biology Reporter - Flavonoids from Ginkgo biloba have antioxidant and free radical scavenging activity. In the present study, we used different concentrations of OS (organic...     

Isolation,characterization, and function analysis of a flavonol synthase gene from <Emphasis Type="Italic">Ginkgo biloba</Emphasis>

Flavonols are produced by the desaturation of dihydroflavanols, which is catalyzed by flavonol synthase (FLS). FLS belongs to the 2-oxoglutarate iron-dependent oxygenase family. The full-length cDNA and genomic DNA sequences of the FLS gene (designated as GbFLS) were isolated from Ginkgo biloba. The full-length cDNA of GbFLS contained a 1023-bp open reading frame encoding a 340-amino-acid protein. The GbFLS genomic DNA had three exons and two introns. The deduced GbFLS protein showed high identities with other plant FLSs. The conserved amino acids (H–X–D) ligating ferrous iron and residues (R–X–S) participating in 2-oxoglutarate binding were found in GbFLS at similar positions like other FLSs. GbFLS was found to be expressed in all tested tissues including roots, stems, leaves, and fruits. Expression profiling analyses revealed that GbFLS expression was induced by all of the six tested abiotic stresses, namely, UV-B, abscisic acid, cold, sucrose, salicylic acid, and ethephon, consistent with the in silico analysis results of the promoter region. The recombinant protein was successfully expressed in the E. coli strain BL21 (DE3) with a pET-28a vector. The in vitro enzyme activity assay by high performance liquid chromatography indicated that recombinant GbFLS protein could catalyze the formation of dihydrokaempferol to kaempferol and the conversion of kaempferol from naringenin, suggesting that GbFLS is a bifunctional enzyme within the flavonol biosynthetic pathway.     

洪湖水体藻类藻相特征及其对生境的响应

藻类是水生态系统的重要成分,它的群落结构、细胞密度变化与水环境相适应,随水环境的变化而改变,因此藻相变化是评价水体质量的一项重要指标。2009—2010年在洪湖水面不同方位布点采样,对水体的浮游藻类藻相(群落结构、密度)和水质状况(水位(water level,H)、水温(water temperature,tw)、透明度(transparency,SD)、总氮(total nitrogen,TN)、总磷(totalphosphorus,TP)、高锰酸盐指数(permanganate index,CODMn)和叶绿素含量(chlorophyll a,Chl-a)等)进行了逐月的调查、监测,采用湖库营养状态指数法对湖泊富营养化评价,并运用多元逐步回归方法建立水体藻类与生境因子的回归方程。结果表明:洪湖水体总体上已达到轻度富营养化状态;藻类以蓝藻门、硅藻门和绿藻门为主,共鉴定出7门65属,藻细胞密度为1.14×106—3.24×107个/L,藻相季节变化特征明显。藻类组成以蓝藻门密度最高(52.93%),硅藻门(25.96%)和绿藻门(16.83%)次之,隐藻门(1.98%)、金藻门(1.64%)、裸藻门(0.42%)和甲藻门(0.25%)相对较低。藻类藻相及优势种在不同季节有所差异,冬春季节(12—5月)以硅藻门的直链藻、小环藻和针杆藻为优势种,夏秋季节(7—11月)以蓝藻门的鱼腥藻和微囊藻为优势种;湖泊藻类细胞密度与tw、CODMn呈正显著相关关系,与H、TN、TP、SD相关关系不显著;藻细胞生长逐步回归方程为y=3.7815+0.0794tw+0.5670CODMn-1.3467SD,藻细胞生长主要受水温和有机污染物等的影响,氮磷不是藻类生长的控制因子;在湖泊不同区域,环境条件存在差异,导致藻类生长过程中起主导作用的环境因子存在一定的差异,蓝藻生长主要受tw、CODMn和SD控制,绿藻生长主要受H、tw和CODMn影响,而硅藻生长决定于水体CODMn。     

EMF基因与植物营养生长

在高等植物中,外源和内源因素共同调控着植物从营养生长到生殖生长的转换。拟南芥EMF1和EMF2基因缺失的突变体不经过任何营养生长,种子萌发后便开花,这说明EMF基因是植物花发育的抑制基因。目前已从水稻、玉米、拟南芥等植物中克隆得到EMF同源基因,但其功能研究大多停留在拟南芥上。研究表明,EMF基因决定着植物营养生长阶段的发育,抑制植物开花。因此,开展EMF基因的分离、克隆和功能研究,有利于阐述植物营养生长过程阶段的抑花机制。对EMF基因的研究进展进行了综述,并提出EMF基因表达调控的闸门模型,以对EMF基因功能的进一步分析提供参考。     

脂联素基因SNP45T／G多态性与2型糖尿病相关性研究

目的：探讨脂联素基因（APM1）SNP45T／G多态性与湖北汉族人群2型糖尿病的相关性。方法：采用聚合酶链反应．限制性片断长度多态性（PCR—RFLP）方法分析了479例样本的APM1基因SNP45T／G多态性,并测定身高、体重、腰围、臀围、血压和空腹血糖等生理指标。结果：两种实验设计中对照组与病例组基因型和等位基因频率差异均无统计学意义。结论：脂联素基因SNP45T／G多态性在湖北汉族人群2型糖尿病的发生发展中可能不起主要作用。     

Linking tree growth and intra-annual density fluctuations to climate in suppressed and dominant Pinus sylvestris L. trees in the forest-steppe of Southern Siberia

Climate change affects forest dynamics with potential consequences for essential ecosystem services. The retrospective analysis of secondary growth unveils the effect of climate on forests. However, most tree-ring studies focus on dominant trees, and less is known about the climatic response of their neighbor suppressed trees. We evaluated the influence of tree social status (dominant/suppressed) on climate response in Pinus sylvestris L. trees from two sites with contrasting water availability conditions in the forest-steppe ecotone in southern Siberia. Tree-ring width and intra-annual density fluctuations (IADFs) were used as proxies. Late spring to early summer conditions were the main climate drivers in both tree social status, but the climate response of suppressed trees was stronger and had a longer time window (May-June). IADFs’ occurrence was controlled by temperature and its frequency was modulated by local conditions, being more common at the dry site, with tree status just marginally significant. Our results suggest that under the projected warmer and drier climate, suppressed trees in southern Siberia will be prone to increased water shortage, leading to possible higher mortality of more sensitive suppressed trees, with potential consequences for carbon sequestration in the forest-steppe ecosystems in southern Siberia.     

Dendrochronological analysis of Sequoia sempervirens in an interior old-growth forest

Dendrochronological studies of large and old Sequoia sempervirens are limited by access and complex crossdating, but core sampling at regular height intervals along the main trunks of five standing trees allowed for reconstruction of growth, height, and age while providing within-tree replication for crossdating. We developed a crossdated ring-width chronology (1453–2015) for redwoods growing in an easternmost old-growth forest in the Napa Range of California, determined aboveground tree attributes, investigated the inter-annual climate-growth relationships since the late 19th century, and documented long-term growth trends. Age, height, f-DBH (functional diameter at breast height), and aboveground biomass of these co-dominant trees ranged from 241 to 783 years, 45.7 to 61.5 m, 117.0 to 226.9 cm, and 9.34 to 33.62 Mg, respectively. Bootstrapped correlation and response function analysis showed radial growth positively related to May through August Palmer Drought Severity Index (PDSI) and negatively related to maximum June temperature (r ≥ │0.47│, P < 0.0001), explaining 33.3% of ring-width variation. Bootstrapped correlations over a moving 40-year window indicated strengthening relationships with PDSI and minimum temperature. The long-term growth trend, reflected by the size-detrended metric of residual wood volume increment (RWVI), varied over time and showed an average one-year decrease of 13.3% for 20th and 21st century droughts. A fire detected in August 1931 corresponded with a one-year decrease in RWVI of 43.1% followed by >100% increase within five years. Growth dynamics for redwoods in this interior forest provide a point of comparison for redwoods previously studied in old-growth forests along the latitudinal gradient, highlighting range-wide trends and site-specific differences in responses to climate and fire.     

香菇基因组中EST-SSR的构成和分布

从真菌基因组计划网站(FGP)和NCBI网站数据库下载了符合条件的总长度为8.1×106bp的11150条香菇的EST(包括10条cDNA)序列,通过SSRhunter1.3软件结合手工查找,从中发现2.83%即316条EST含有一共469个SSR,平均每17.3kb出现一个EST-SSR。在所有EST-SSR中,三碱基和六碱基SSR出现最多,分别占EST-SSR总数的38.00%和20.00%。出现较多的基序为(A)n、(T)n、(GA)n、(AG)n、(TGA)n、(GAT)n和(TCTTT)n,占所有EST-SSR的35.39%。     

A flow-injection chemiluminescence method for the determination of human serum albumin, using the reaction of fluorescein-human serum albumin-sodium hypochlorite by the enhancement effect of the cationic surfactant cetyltrimethylammonium bromide.

The interaction between surfactant and fluorescein was studied, using a fluorescence spectroscopy and flow-injection (FI) chemiluminescence (CL) method. It was found that the cationic surfactant cetyltrimethylammonium bromide (CTAB) could cause the structural transformation of fluorescein from the quinone to the spirolactone form, and greatly enhance the CL intensity of the fluorescein-human serum albumin (HSA) complex. Based on this finding, a rapid and sensitive FI-CL method was developed for the determination of HSA. Under the optimum conditions, the proposed method has a linear range of 0.05-24.0 microg/mL, with a detection limit of 0.03 microg/mL for HSA (3sigma). The relative standard deviation (RSD) of 1.2 microg/mL HSA (n = 8) is 0.8%. The method was applied to the determination of protein content in urine samples, with satisfactory results. Density functional theory was used to study the mechanism of surfactant-enhanced CL intensity of the fluorescein-HSA complex.     

The spatial pattern of grassland aboveground biomass on Xizang Plateau and its climatic controls

Aims Grassland is the most widely distributed vegetation type on the Xizang Plateau. Accurate remote sensing estimation of the grassland aboveground biomass (AGB) in this region is influenced by the types of vegetation indexes (VIs) used, the grain size (resolution) of the remote sensing data and the targeted ecosystem features. This study attempts to answer the following questions: (i) Which VI can most accurately reflect the grassland AGB distribution on the Xizang Plateau? (ii) How does the grain size of remote sensing imagery affect AGB reflection? (iii) What is the spatial distribution pattern of the grassland AGB on the plateau and its relationship with the climate?Methods We investigated 90 sample sites and measured site-specific AGBs using the harvest method for three grassland types (alpine meadow, alpine steppe and desert steppe). For each sample site, four VIs, namely, Normalized Difference VI (NDVI), Enhanced VI, Normalized Difference Water Index (NDWI) and Modified Soil-Adjusted VI (MSAVI) were extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS) products with grain sizes of 250 m and 1 km. Linear regression models were employed to identify the best estimator of the AGB for the entire grassland and the three individual grassland types. Paired Wilcoxon tests were applied to assess the grain size effect on the AGB estimation. General linear models were used to quantify the relationships between the spatial distribution of the grassland AGB and climatic factors.Important findings The results showed that the best estimator for the entire grassland AGB on the Xizang Plateau was MSAVI at a 250 m grain size (MSAVI 250 m). For each individual grassland type, the best estimator was MSAVI at a grain size of 250 m for alpine meadow, NDWI at a grain size of 1 km for alpine steppe and NDVI at a grain size of 1 km for desert steppe. The explanation ability of each VI for the grassland AGB did not significantly differ for the two grain sizes. Based on the best fit model (AGB =^-10.80 + 139.13 MSAVI 250 m), the spatial pattern of the grassland AGB on the plateau was characterized. The AGB varied from 1 to 136g m ?2. Approximately 59% of total spatial variation in the AGB for the entire grassland was explained by the combination of the mean annual precipitation (MAP) and mean annual temperature. The explanatory power of MAP was weaker for each individual grassland type than that for the entire grassland. This study illustrated the high efficiency of the VIs derived from MODIS data in the grassland AGB estimation on the Xizang Plateau due to the vegetation homogeneity within a 1×1 km pixel in this region. Furthermore, MAP is a primary driver on the spatial variation of AGB at a regional scale.